There's your problem! But why and more......
Discussion
Right, got your cup of coffee and biscuits? Then I'll begin.....
Finally got around to stripping the motor to find the reasons behind the low comp on cylinder 4 and oil blowing out of the breather and as suspected, it's a broken top ring on no.4, BUT the piston is also broken; a piece about 20mm between the top and second top ring is broken away. I was deciding whether to check the other 3 as compression was good on those. Pleased I did as no.2 has a broken top ring too.
Now I have fitted pistons before without problems so (hopefully) it's not total incompetance. So why this time. The pistons are AE21253 +060 CAN, came supplied by the machine shop who did the rebore, the engine was run in in the correct manner, the only thing I wonder about is the compression ratio. The car has a standard (as far as I know) MG Metro head but the block was decked 20thou to bring the pistons RIGHT to the top of the bore although not (I believe) high enough to hit the head, there is the thickness of the gasket in there. The car did pink on hills under load and tended to run on quite a bit when hot.
So before I rebuild, I need to ascertain why it went bang after less than 2000 miles. The car has been driven fairly hard and with a diff ratio of 3.1 would reach about 96 or 97 mph reading on a standard clubman 2 clock dash. (I wonder if that was under reading as I suspect the old 998 had a lower diff ratio, but I used to think it was reasonably accurate). (Different size wheels on an Metro to an old Clubman too. Car currently running on 12" with 60 profile or 10" with 70 profile). (No rev counter I'm afraid so could have been over revved).
Once I get this sorted, I am wondering about any improvements while the engine is out. Gearbox used to crunch into reverse but was otherwise ok. Thought about cross pin diff as I understand a LSD as well as being more expensive is a bit of a bugger on a mini. The car was originally put together with the intention of doing Historic and Club Rallies but may go to hill climbs instead, ignoring my thread of a few months ago for a few minutes, where I was wondering about making it an economical, decent mpg car. Recent opinion on here reckoned that an uprated diff meant that the drop gears would go instead, but Mr Calver states that the standard drop gears are ok for most applications such as my own. Rather than strip and rebuild my box, is it cheaper and easier in the long run getting a rebuilt unit with the diff fitted?
Thought about a more performance orientated cam, say a 286 or scatter cam instead of the Minispares Evolution one but Minispares really do reckon their cam is a good one and as torque is as important as outright power both on rallies (where the stages are often short farmyard thrashes, a bit autotesty) and hills, maybe they are right. A modified head was always No 1 on an A series upgrade but I thought the MG head was a good one, certainly the valve sizes are larger than many "Stage 3" heads currently sold. Not sure if they drop a valve size to allow for unleaded seats, hopefully someone could enlighten me. Finally (sigh of relief from those still with me) I need a decent dizzy (Aldon) and thinking about changing the carb. I know the HIF44 is highly though of but the one I have seems to be a little worn and troublesome. Love the idea of a Weber 45, simple once set up, but not the idea of a battery box on the dashboard, so suspect 2x1.5 SU's, which a well known contributor to this site reckons are almost as good except at the ultimate top end, but do need constant fiddling if my old MG Midgets and MGB are anything to go by.
Thank for listening, I hope if you got to the end of this you may be able to offer some advice. Have to add that money is tight at present, due to work problems but at least it's given me time to get this started.
regards
Tony H
Finally got around to stripping the motor to find the reasons behind the low comp on cylinder 4 and oil blowing out of the breather and as suspected, it's a broken top ring on no.4, BUT the piston is also broken; a piece about 20mm between the top and second top ring is broken away. I was deciding whether to check the other 3 as compression was good on those. Pleased I did as no.2 has a broken top ring too.
Now I have fitted pistons before without problems so (hopefully) it's not total incompetance. So why this time. The pistons are AE21253 +060 CAN, came supplied by the machine shop who did the rebore, the engine was run in in the correct manner, the only thing I wonder about is the compression ratio. The car has a standard (as far as I know) MG Metro head but the block was decked 20thou to bring the pistons RIGHT to the top of the bore although not (I believe) high enough to hit the head, there is the thickness of the gasket in there. The car did pink on hills under load and tended to run on quite a bit when hot.
So before I rebuild, I need to ascertain why it went bang after less than 2000 miles. The car has been driven fairly hard and with a diff ratio of 3.1 would reach about 96 or 97 mph reading on a standard clubman 2 clock dash. (I wonder if that was under reading as I suspect the old 998 had a lower diff ratio, but I used to think it was reasonably accurate). (Different size wheels on an Metro to an old Clubman too. Car currently running on 12" with 60 profile or 10" with 70 profile). (No rev counter I'm afraid so could have been over revved).
Once I get this sorted, I am wondering about any improvements while the engine is out. Gearbox used to crunch into reverse but was otherwise ok. Thought about cross pin diff as I understand a LSD as well as being more expensive is a bit of a bugger on a mini. The car was originally put together with the intention of doing Historic and Club Rallies but may go to hill climbs instead, ignoring my thread of a few months ago for a few minutes, where I was wondering about making it an economical, decent mpg car. Recent opinion on here reckoned that an uprated diff meant that the drop gears would go instead, but Mr Calver states that the standard drop gears are ok for most applications such as my own. Rather than strip and rebuild my box, is it cheaper and easier in the long run getting a rebuilt unit with the diff fitted?
Thought about a more performance orientated cam, say a 286 or scatter cam instead of the Minispares Evolution one but Minispares really do reckon their cam is a good one and as torque is as important as outright power both on rallies (where the stages are often short farmyard thrashes, a bit autotesty) and hills, maybe they are right. A modified head was always No 1 on an A series upgrade but I thought the MG head was a good one, certainly the valve sizes are larger than many "Stage 3" heads currently sold. Not sure if they drop a valve size to allow for unleaded seats, hopefully someone could enlighten me. Finally (sigh of relief from those still with me) I need a decent dizzy (Aldon) and thinking about changing the carb. I know the HIF44 is highly though of but the one I have seems to be a little worn and troublesome. Love the idea of a Weber 45, simple once set up, but not the idea of a battery box on the dashboard, so suspect 2x1.5 SU's, which a well known contributor to this site reckons are almost as good except at the ultimate top end, but do need constant fiddling if my old MG Midgets and MGB are anything to go by.
Thank for listening, I hope if you got to the end of this you may be able to offer some advice. Have to add that money is tight at present, due to work problems but at least it's given me time to get this started.
regards
Tony H
Skyedriver said:
...The car did pink on hills under load ..... The car has been driven fairly hard ... it went bang after less than 2000 miles...
I may have misinterpreted you but if the above clipped quote is accurate? then I'm not surprised it went bang!Pinking is detonation (- an explosive combustion), usually due to too much ignition advance, basically you've beeen bashing the top of your pistons for 2000mls - almost certain to break them.
I don't mean to be abrupt but if you want an engine to last, you've really got to build it correctly and set it up right in the first place, no manner of different cams or other bits will make up for not getting the build spot on.
Edited by Dino42 on Saturday 13th September 23:59
Tony,
I think it's a distributor problem which has led to the failures.
If you have it advanced for max power at high revs, it could well be that you have too much advance in the mid-range.
Go for an Aldon 'Red' unit which has a lot of mechanical advance and get it set on a rolling road. Alternatively, call Aldon and they will tell you what static advance to set and do this EXACTLY right. I assume you have no vac adv/ret.
As Dino said, it's the detonation that's caused the rings, then the pistons to fail. The 21253 is a really excellent production piston. But make sure you replace all of them as the others could be on the point of failure.
Peter
I think it's a distributor problem which has led to the failures.
If you have it advanced for max power at high revs, it could well be that you have too much advance in the mid-range.
Go for an Aldon 'Red' unit which has a lot of mechanical advance and get it set on a rolling road. Alternatively, call Aldon and they will tell you what static advance to set and do this EXACTLY right. I assume you have no vac adv/ret.
As Dino said, it's the detonation that's caused the rings, then the pistons to fail. The 21253 is a really excellent production piston. But make sure you replace all of them as the others could be on the point of failure.
Peter
Always worried about the pinking BUT it wasn't all the time, just if you started to labour up a hill. Timing was set static at if I remember off the top of my head, 4 degrees which was the MG Metro standard setting,
but if that's my problem then at least we've got to the bottom of it and thanks.
No vacuum advance either. Had occasional pinking before on other engines but never had a problem like this one.
but if that's my problem then at least we've got to the bottom of it and thanks.
No vacuum advance either. Had occasional pinking before on other engines but never had a problem like this one.
Burette your head. Make sure you have all the components parts CC values (Piston dish, Ring land to pistons top, Head gasket compressed) and get an accurate unswept volume. No good guessing what CR you are running. As has been alluded to on here, a combination of pre-ignition and CR has done for your pistons.
Standard MG Metro ran 10.4 to 1 CR out of factory - early ones on leaded juice went better than the later ones that had the ignition retarded to use unleaded (!) - this is key to your problem. If the block has been decked and the pistons are now flush your CR could be around 11+ to 1. If you've been using 95 octane unleaded this will have compounded your problem.
Tony - Get all the facts down and we'll do our best on here to help you sort it.
PS - Get the HIF44 rebuilt properly and don't mess about with twins. I'm sure some will disagree but twin SU's just aren't worth the trip. If you want more intake potential than an HIF44 just modify the bulkhead and go straight down the 45DCOE route.
Standard MG Metro ran 10.4 to 1 CR out of factory - early ones on leaded juice went better than the later ones that had the ignition retarded to use unleaded (!) - this is key to your problem. If the block has been decked and the pistons are now flush your CR could be around 11+ to 1. If you've been using 95 octane unleaded this will have compounded your problem.
Tony - Get all the facts down and we'll do our best on here to help you sort it.
PS - Get the HIF44 rebuilt properly and don't mess about with twins. I'm sure some will disagree but twin SU's just aren't worth the trip. If you want more intake potential than an HIF44 just modify the bulkhead and go straight down the 45DCOE route.
Edited by FWDRacer on Monday 15th September 08:27
tony
pinking or detonation has broken your pistons, the 21253 is a great piston, the mighty minis use them as a piston with no issues and a lot of people use them (with some mods) as a cheap turbo piston. as a std piston they seem to run 10:1 happily for ages
id guess that the dizzy is the main issue, what sort was it and what advance was it running?
happy days!
pinking or detonation has broken your pistons, the 21253 is a great piston, the mighty minis use them as a piston with no issues and a lot of people use them (with some mods) as a cheap turbo piston. as a std piston they seem to run 10:1 happily for ages
id guess that the dizzy is the main issue, what sort was it and what advance was it running?
happy days!
Castrol Valvemaster Plus, which has an octane booster, helps with higher CR's too. This standard 95 octane unleaded really is a bit too low on octane for an engine like yours. With Valvemaster plus added to super unleaded you should be able to run at least 10.8:1 with no problems. I run 11.2:1 on my 'S' with that petrol mix and I have an Aldon customised dizzy.
I've just re-read your initial post. You mention you have an MG Metro head with 35mm inlet/29mm exhaust and you are right in saying these are bigger than standard. If the head isn't modified, you can do a pretty effective job on these heads by blending in the short side radius of both inlet and exhaust ports and removing, blending and smoothing the casting in the area of the valve seat and Valve guide. A good home job will release some potential from the bigger valve set-up even with standard shape combustion chambers.
It cost nothing but time and a sooty face
It cost nothing but time and a sooty face
Hello and thanks for your replies, some of which are blunt and (quite rightly) to the point. Nerve hit!
The head was a standard MG Metro, as far as I know (not too sure of its pedigree. The block standard MG Metro +60 thou and decked 20 thou. Again pedigree unknown. The carb was a HIF44 running on unleaded but with Valvemaster Plus. Exhaust = LCB.
Distributor again MG Metro as far as I know, set at standard MG Metro static as far as I remember, played around with timing and think my preferred was 4 degrees before, to attempt to eliminate run on after switching off and pinking. The distributor DID have vacuum advance (sorry about previous posting) but disconnecting made little difference.
The engine was bought second hand as an exMG Matro unit, stripped and basically rebuilt plus 60 thou. so didn't think the old distributor was going to cause this, how wrong can you be.
Maybe it's been a bitza engine that I have unknowingly over worked.
Not sure of my route now, may look for a built, tuned s/h unit, or standard MG or may start again with this one. New bits total cost may equal s/h built unit, but will only buy s/h if I can test it first.
Edited to add (previously written in a hurry with young lad pulling at the keyboard.)
New pistons around £140, I would replace the front plate and timing cover as they are worn, damaged and suspect; around £60. Add to that a gasket set. I am worried that the gearbox, currently crunching reverse is going to deteriorate and will need replacing soon and my costs mount rapidly. Currently in a state of financial uncertainty and living a long way from anywhere to use the completed car in competition and I begin to wonder the best way forward. Plenty of time to decide though. Second hand items are thin on the ground up here but buying new has a big implication regarding delivery costs as carriers run up "telephone numbers" on the bill.
Thanks again
The head was a standard MG Metro, as far as I know (not too sure of its pedigree. The block standard MG Metro +60 thou and decked 20 thou. Again pedigree unknown. The carb was a HIF44 running on unleaded but with Valvemaster Plus. Exhaust = LCB.
Distributor again MG Metro as far as I know, set at standard MG Metro static as far as I remember, played around with timing and think my preferred was 4 degrees before, to attempt to eliminate run on after switching off and pinking. The distributor DID have vacuum advance (sorry about previous posting) but disconnecting made little difference.
The engine was bought second hand as an exMG Matro unit, stripped and basically rebuilt plus 60 thou. so didn't think the old distributor was going to cause this, how wrong can you be.
Maybe it's been a bitza engine that I have unknowingly over worked.
Not sure of my route now, may look for a built, tuned s/h unit, or standard MG or may start again with this one. New bits total cost may equal s/h built unit, but will only buy s/h if I can test it first.
Edited to add (previously written in a hurry with young lad pulling at the keyboard.)
New pistons around £140, I would replace the front plate and timing cover as they are worn, damaged and suspect; around £60. Add to that a gasket set. I am worried that the gearbox, currently crunching reverse is going to deteriorate and will need replacing soon and my costs mount rapidly. Currently in a state of financial uncertainty and living a long way from anywhere to use the completed car in competition and I begin to wonder the best way forward. Plenty of time to decide though. Second hand items are thin on the ground up here but buying new has a big implication regarding delivery costs as carriers run up "telephone numbers" on the bill.
Thanks again
Edited by Skyedriver on Monday 15th September 19:18
Just sitting down and licking my wounds.
Super unleaded : wonder where my nearest supplier is? May be Inverness (100 miles way)
Rolling Road : ditto possibly or may be farther afield
The joys of living in a beautiful remote area have some pitfalls
Super unleaded : wonder where my nearest supplier is? May be Inverness (100 miles way)
Rolling Road : ditto possibly or may be farther afield
The joys of living in a beautiful remote area have some pitfalls
Edited by Skyedriver on Friday 19th September 09:50
It must be difficult to be so far from civilisation!
Normally I would never recommend fitting a second-hand engine without first doing a full re-build inc a re-bore and crank grind. However, in your case it might be better to find a used unit, although I would still strip it and probably replace the big-ends, mains, thrusts and oil pump as these are low-cost, easy to fit and will give you confidence. You could also lightly hone the bores and, maybe, fit new rings so long as the bores are not too worn.
However, by the time you do all this, you could probably get your existing block re-bored, new 21253 pistons, a micro-polish of the crank may be fine (you can do this yourself), fit all new bearings and thrusts plus an oil pump and you'll have, effectively, a completely new engine.
Guru1071's mail order service is great - next day usually - and you can measure everything before ordering the new bits. For example, measure the end float and order the correct thrust bearings to give a minimum of 1.5 thou end float and a max of 4 thou.
Whilst it's all down it could be worth doing the gearbox. Personally I hate doing boxes and usually use a transmission specialist. You will have carriage each way, but at least you'll know it's right when re-fitting it.
I hope all this helps and doesn't just cause more uncertainty.
Peter
Normally I would never recommend fitting a second-hand engine without first doing a full re-build inc a re-bore and crank grind. However, in your case it might be better to find a used unit, although I would still strip it and probably replace the big-ends, mains, thrusts and oil pump as these are low-cost, easy to fit and will give you confidence. You could also lightly hone the bores and, maybe, fit new rings so long as the bores are not too worn.
However, by the time you do all this, you could probably get your existing block re-bored, new 21253 pistons, a micro-polish of the crank may be fine (you can do this yourself), fit all new bearings and thrusts plus an oil pump and you'll have, effectively, a completely new engine.
Guru1071's mail order service is great - next day usually - and you can measure everything before ordering the new bits. For example, measure the end float and order the correct thrust bearings to give a minimum of 1.5 thou end float and a max of 4 thou.
Whilst it's all down it could be worth doing the gearbox. Personally I hate doing boxes and usually use a transmission specialist. You will have carriage each way, but at least you'll know it's right when re-fitting it.
I hope all this helps and doesn't just cause more uncertainty.
Peter
Skyedriver said:
Just sitting down and licking my wounds.
Super unleaded : wonder where my nearest supplier is? May be Inverness (100 miles way)
Rolling Road : ditto possibly or may be farther afield
The joys of living in a beautiful remote area have some pitfalls
Better alternative than super unleaded is (if you can get some) about 10% toluene in regular unleaded will give you 100-110 octane fuel.Super unleaded : wonder where my nearest supplier is? May be Inverness (100 miles way)
Rolling Road : ditto possibly or may be farther afield
The joys of living in a beautiful remote area have some pitfalls
Edited by Skyedriver on Friday 19th September 09:50
Toluene is the best octane booster there is, downside is it's rather carcinogenic, which is why they don't add it at the pump. Don't bother adding any other octane boosters, as many of the non-aromatic octane boosters will be deactivated by the toluene.
As an aside, the turbo F1 cars of the 80s ran toluene as a fuel, hence the mega boost levels.
You'd have to be nuttier than squirrel sh!t to mess about with Toluene, let alone use it merrily as a day-to-day fuel additive. Very nasty stuff - have a look on Wikipedia.
wikipedia said:
Serious adverse behavioural effects are often associated with toluene abuse related to the deliberate inhalation of solvents. Long term toluene exposure is often associated with effects such as: psychoorganic syndrome; visual evoked potential (VEP) abnormality; toxic polyneuropathy, cerebellar, cognitive, and pyramidal dysfunctions; optic atrophy; and brain lesions.
Toluene causes postural tremors by increasing extracellular concentrations of ã-aminobutyric acid (GABA) within the cerebellar cortex. Treatment with GABA agonists such as, benzodiazepines provide some relief from toluene induced tremor and ataxia. An alternative to drug treatment is vim thalamotomy. The tremors associated with toluene misuse do not seem to be a transient symptom, but an irreversible and progressive symptom which continues after solvent abuse has been discontinued.
There is some evidence that low level toluene exposure may cause disruption in the differentiation of astrocyte precursor cells. This does not appear to be a major hazard to adults; however, exposure of pregnant women to toluene during critical stages of fetal development could cause serious disruption to neuronal development.
Toluene causes postural tremors by increasing extracellular concentrations of ã-aminobutyric acid (GABA) within the cerebellar cortex. Treatment with GABA agonists such as, benzodiazepines provide some relief from toluene induced tremor and ataxia. An alternative to drug treatment is vim thalamotomy. The tremors associated with toluene misuse do not seem to be a transient symptom, but an irreversible and progressive symptom which continues after solvent abuse has been discontinued.
There is some evidence that low level toluene exposure may cause disruption in the differentiation of astrocyte precursor cells. This does not appear to be a major hazard to adults; however, exposure of pregnant women to toluene during critical stages of fetal development could cause serious disruption to neuronal development.
Edited by FWDRacer on Monday 22 September 10:33
I'm not surprised to hear of the fuel guys - sad, but not surprised. They moved on to using cubane as a fuel for trials after toluene 
Don't think that lasted long though...
In my previous career as a research chemist, it was a widely used solvent, not something that is considered overly hazardous by lab standards. Having said that, my life expectancy jumped considerably when I stopped being a research chemist!!!!!
But all aromatics are not to be messed with, they are hazardous to greater or lesser amounts, but all make good octane boosters.
Edited to add that the Wiki refers to solvent abuse - deliberately inhaling aromatics is phenominally stupid, and quite different to using it as a fuel additive (unless you've got a leaky tank and poor ventilation).... Still best to be careful though.
Don't think that lasted long though...In my previous career as a research chemist, it was a widely used solvent, not something that is considered overly hazardous by lab standards. Having said that, my life expectancy jumped considerably when I stopped being a research chemist!!!!!
But all aromatics are not to be messed with, they are hazardous to greater or lesser amounts, but all make good octane boosters.
Edited to add that the Wiki refers to solvent abuse - deliberately inhaling aromatics is phenominally stupid, and quite different to using it as a fuel additive (unless you've got a leaky tank and poor ventilation).... Still best to be careful though.
Edited by Fatboy on Monday 22 September 20:50
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